1. Field of the Invention
The present invention relates to electronic circuits, and, more particularly, to buffers in digital electronic circuits.
2. Description of the Related Art
Generally, semi-conductor memory devices include a data output buffer which has large current driving capability to increase fan-out of data output to terminals connected thereto. A typical data output buffer includes pull-up devices and pull-down devices connected in series between a supply voltage line and a ground line. Such a data output buffer applies a supply voltage to a data output terminal connected to the node of the data output buffer through the pull-up device for outputting a high level of data output. And the data output buffer couples ground potential to a data output terminal connected to the node of the data output buffer through a pull-down device for outputting a low level of data output is outputted.
Integrated CMOS logic circuits exist in two basic varieties: static and dynamic CMOS field-effect transistor ("FET") logic gates. Both varieties have at least one input and at least one output. A static CMOS logic gate typically requires no external clock signal to control its operation. Moreover, the static CMOS logic gate can preserve its state for as long as the power supply is applied to it. A dynamic CMOS logic gate, on the other hand, typically does not hold its state indefinitely and requires an external clock signal for its operation. The external clock defines alternating periods of precharging and evaluating the logic gate. Static CMOS circuits, on the other hand, evaluate and then hold the state until the next cycle.
Each of these circuit families has its own advantages and disadvantages. Dynamic circuits are fast, but they are also susceptible to noise. Static circuits are slower than dynamic circuits, but they typically have greater noise immunity and prevention of signal dissipation by strongly holding the output to a power rail voltage. It would be desirable to combine the benefits of these different circuit families without also incorporating their disadvantages.